Adolescence is a critical neurodevelopmental period associated with dramatic increases in rates of substance use. Identifying the pathways to substance use and its effects on child and adolescent development is critically important, as the effects of substance use during ongoing maturation likely have long-lasting effects on brain functioning and behavioral, health, and psychological outcomes. This Research Project Site application from SRI International is in response to RFA-DA-15-015 as part of the ABCD-USA Consortium (10/13), to prospectively determine the neurodevelopmental and behavioral predictors and consequences of substance use on children and adolescents. A representative community sample of 550 9-10 year olds enriched for high- risk characteristics will be recruited, contributing to the sample of 11,111 to be collected from 11 hubs across the ABCD-USA Consortium. All participants will undergo a comprehensive baseline assessment, including state-of-the-art brain imaging, comprehensive neuropsychological testing, bioassays, mobile monitoring and careful assessment of substance use, environment, psychopathological symptoms, and social functioning every 2 years. Interim annual interviews and quarterly web-based assessments will provide refined temporal resolution of behaviors, development, and life events with minimal participant burden. These Consortium-wide data obtained during the course of this project will elucidate: 1) the effects of substance use patterns on the adolescent brain; 2 the effects of substance use on behavioral and health outcomes; 3) the bidirectional relationship between psychopathology and substance use patterns; 4) the effects of individual genetic, behavioral, neurobiological, and environmental differences on risk profiles and substance use outcomes; and 5) the gateway interactions between use of different substances. Our project focuses on the sleep and chronobiology data collected across the consortium, both with questionnaires and periodic assessment with wearable wrist trackers. Our aims are to assess sleep behavior and chronotype as predictors of subsequent substance use, and to investigate the effects of current substance use on sleep characteristics in adolescents. We will also conduct exploratory analyses to determine the effect of marijuana usage on sleep, to evaluate relationships between sleep and chronobiology variables, substance use and development of depression; and to investigate genetic and environmental contributions to associations between sleep characteristics, chronotype and substance use in twins. The combination of careful assessment of subjective and objective sleep and chronotype, detailed evaluation of substance use patterns and sensitive clinical measures will provide a unique resource for the scientific community, and help guide age-appropriate behavioral interventions.